This invention relates to wind turbines more particularly an improved method of harnessing wind power thereby converting kinetic energy to generate electrical energy.
Windmills have been known and used for centuries as power generators and typically have been used to pump water and to grind grains such as wheat and corn. Because energy from the wind is free and non-polluting, much attention has been given to improving the efficiency and lowering the cost of windmill structures. Wind power has increased exponentially since the dawn of the 21st century. The amount of power that a conventional or propeller type windmill can generate is directly proportional to the square of the diameter of the circle of rotation of the blade tips and also to the cube of the wind velocity.
A wind turbine converts kinetic energy from the wind into electrical power. Generally, wind turbines have a main rotor shaft operationally coupled to an electrical power generator that sits atop a tower that is pointed into the direction of the wind. In one embodiment the horizontal-axis wind turbines (HAWT) have the main rotor shaft arranged horizontally. Conventional HAWTs wind turbines have three blades and are oriented or pointed into the wind by computer controlled motors. These turbines typically require a supporting tower ranging from 60 to 90 meters (200 to 300 feet) in height. The blades generally rotate at a rotational speed of about 10 to 22 rpm. A gear box is commonly used to step up the speed to drive the generator. In other embodiments the vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically.
As wind blows past a turbine, the blades capture the energy and rotate. This rotation triggers an internal shaft to spin, which is connected to a gearbox increasing the speed of rotation, which connects to a generator that ultimately produces electricity. Most commonly, wind turbines consist of a steel tubular tower, of at least 100 feet, which supports both a “hub” securing wind turbine blades and the “nacelle” which houses the turbine's shaft, gearbox, generator and controls. A wind turbine is equipped with wind assessment equipment and will automatically rotate into the face of the wind, and angle or “pitch” its blades to optimize energy capture.
Although HAWTs have achieved widespread usage, their efficiency is not optimized. In particular, they will not exceed the Betz limit of 59.3% efficiency in capturing the potential energy of the wind passing through it. More energy can be collected by using a variable speed turbine and a solid state power converter to interface the turbine with the generator. It is desirable to provide a lighter structure to support HAWT or VAWT wind turbines to save on manufacturing and maintenance costs.